Richard C. Brunken

Reversibility of cardiac wall-motion abnormalities predicted by positron tomography.

Positron emission tomography (PET) can be used with nitrogen-13-ammonia (13NH3) to estimate regional myocardial blood flow, and with fluorine-18-deoxyglucose (18FDG) to measure exogenous glucose uptake by the myocardium. We used PET to predict whether preoperative abnormalities in left ventricular wall motion in 17 patients who underwent coronary-artery bypass surgery were reversible. The abnormalities were quantified by radionuclide or contrast angiography or both, before and after grafting. PET images were obtained preoperatively. Abnormal wall motion in regions in which PET images showed preserved glucose uptake was predicted to be reversible, whereas abnormal motion in regions with depressed glucose uptake was predicted to be irreversible. According to these criteria, abnormal contraction in 35 of 41 segments was correctly predicted to be reversible (85 percent predictive accuracy), and abnormal contraction in 4 of 26 regions was correctly predicted to be irreversible (92 percent predictive accuracy). In contrast, electrocardiograms showing pathological Q waves in the region of asynergy predicted irreversibility in only 43 percent of regions. We conclude that PET imaging with 13NH3 to assess blood flow and 18FDG to assess the metabolic viability of the myocardium is an accurate method of predicting potential reversibility of wall-motion abnormalities after surgical revascularization.

Quantitative Relation Between Myocardial Viability and Improvement in Heart Failure Symptoms After Revascularization in Patients With Ischemic Cardiomyopathy

BACKGROUND Studies of patients with coronary artery disease and left ventricular dysfunction have shown that preoperative quantification of myocardial viability may be clinically useful to identify those patients who will benefit most from revascularization both functionally and prognostically. However, the relation between preoperative extent of viability and change in heart failure symptoms has not been documented carefully. We assessed the relation between the magnitude of improvement in heart failure symptoms after coronary artery bypass surgery (CABG) and the extent of myocardial viability as assessed by use of quantitative analysis of preoperative positron emission tomography (PET) images. METHODS AND RESULTS We studied 36 patients with ischemic cardiomyopathy (mean left ventricular ejection fraction, 28 +/- 6%) undergoing CABG. Preoperative extent and severity of perfusion abnormalities and myocardial viability (flow-metabolism mismatch) were assessed by use of quantitative analysis of PET images with 13N ammonia and fluorine-18-deoxyglucose. Each patients functional status was determined before and after CABG by use of a Specific Activity Scale. Mean perfusion defect size and severity were 63 +/- 13% and 33 +/- 12%, respectively. Total extent of a PET mismatch correlated linearly and significantly with percent improvement in functional status after CABG (r = .87, P < .0001). A blood flow-metabolism mismatch > or = 18% was associated with a sensitivity of 76% and a specificity of 78% for predicting a change in functional status after revascularization. Patients with large mismatches (> or = 18%) achieved a significantly higher functional status compared with those with minimal or no PET mismatch (< 5%) (5.7 +/- 0.8 versus 4.9 +/- 0.7 metabolic equivalents, P = .009). This resulted in an improvement of 107% in patients with large mismatches compared with only 34% in patients with minimal or no PET mismatch. CONCLUSIONS In patients with ischemic cardiomyopathy, the magnitude of improvement in heart failure symptoms after CABG is related to the preoperative extent and magnitude of myocardial viability as assessed by use of PET imaging. Patients with large perfusion-metabolism mismatches exhibit the greatest clinical benefit after CABG.

Influence of age and hemodynamics on myocardial blood flow and flow reserve.

BackgroundAging is associated with changes of the systolic blood pressure that may increase cardiac work and myocardial blood flow at rest and reduce the myocardial flow reserve. This might be misinterpreted as age-related impairment of the coronary vasodilator capacity. Methods and ResultsMyocardial blood flow was quantified at rest and after administration of intravenous dipyridamole in 40 healthy volunteers (12 women and 28 men) with 13N-ammonia and positron emission tomography. Eighteen of the normal subjects were less than and 22 were older than 50 years (31G

Regional perfusion, glucose metabolism, and wall motion in patients with chronic electrocardiographic Q wave infarctions: evidence for persistence of viable tissue in some infarct regions by positron emission tomography.

9 versus 64

Long-term survival of patients with coronary artery disease and left ventricular dysfunction: Implications for the role of myocardial viability assessment in management decisions

9 years). The resting rate-pressure product was lower in the younger than in the older subjects (6895

Positron emission tomography detects tissue metabolic activity in myocardial segments with persistent thallium perfusion defects

1070 versus 8634+1890; p<0.01). Myocardial blood flow at rest averaged 0.76

Regional myocardial metabolism in patients with acute myocardial infarction assessed by positron emission tomography

0.17 mL min1 g1 in the younger volunteers and 0.92

Comparison of maximal myocardial blood flow during adenosine infusion with that of intravenous dipyridamole in normal men

0.25 mL. min1 g1 in the older volunteers (p< 0.05). Hyperemic blood flows did not differ between younger and older subjects (3.0+0.8 versus 2.7

Patient management after noninvasive cardiac imaging: Results from SPARC (Study of myocardial perfusion and coronary anatomy imaging roles in coronary artery disease)

0.6 mL* min1 g-1 p=NS); however, minimal coronary resistance was higher in the older subjects. Corrected for indexes of coronary driving pressure, hyperemic flow was lower in older than in younger normal subjects. The higher resting blood flows combined with similar hyperemic flows resulted in a lower myocardial flow reserve in the older than in the younger normal subjects (4.1

Myocardial Viability Testing and the Effect of Early Intervention in Patients With Advanced Left Ventricular Systolic Dysfunction

0.9 versus 3.0+0.70; p< 0.0001). The flow reserve was more closely correlated with resting than with hyperemic blood flows. ConclusionsAging does not alter significantly dipyridamole-induced hyperemic flows; although coronary vascular resistance after dipyridamole was somewhat increased in older subjects. The gradual decline of the myocardial blood flow reserve correlates with an age-related increase of baseline myocardial work and blood flow. These findings suggest that the reduced flow reserve with age is primarily due to increased cardiac work and blood flow at rest rather than to an abnormal vasodilator capacity.